Lab Coats have a long history in the annals of comedy. Somebody, a long time ago, decided that a doctor in a lab coat could be just as funny as a clown in makeup or a straight-man wearing a suit.
This is especially true for animated shows. For decades animated shows have cast doctors in the role of comedic fodder, usually as slightly inept professionals who are always there with a funny line or a comical diagnosis. For a perfect example of this type of character you have to look no further then Julius Hibbert, the resident physician at Springfield Hospital on the hit animated show The Simpsons.
Modeled after Bill Cosby’s character on the Cosby Show, creators even went as far as to give Dr. Hibbert a pension for colorful sweaters and children who resemble Cosby’s on-screen progeny. Dr. Hibbert is a smart man, though he has a tendency to laugh even at the most tragic news. Most of his comedy comes from either comedic diagnosis, or clever one-liners, which vary form person to person. He is a doctor but also seems to be a pediatrician and a surgeon (he has performed surgery on Homer Simpson several time). He seems to be a good father, fairly ethical (though a tool for the HMO circuit) and has hairstyles that reflect famous black actors depending on which decade you see him (dreadlocks, a Mr. T flattop, etc.).
On Family Guy, the resident doctor is a much more inept doctor than Mr. Hibbert is. His running joke is that when giving diagnosis he always mentions whatever bad stuff is on his mind before getting to the actual information (for example: when telling Peter Griffin what his cancer test said he starts by noting “No, no, this isn’t very good at all…”. After a brief pause he then holds up a picture that his son drew “This doesn’t look like me at all”). He seems to kind of know what he’s doing, though he has a tendency to be too stupid to be believable at most times (putting his hand in a used needle draw thinking it’s where he keeps his rubber gloves).
Not often do you see a lobster- like alien wearing a lab coat, but that’s exactly what you saw if you were a fan of Futurama which aired on FOX in 2000-2003. The running joke with Zoidberg, besides the fact that he was broke and…ummm… had claws… was that he was a terrible doctor usually giving wrong diagnosis or, because it was the future, curing them in weird ways. Frankly, he was hilarious, and just the latest in a long line of funny doctors on animated TV shows.